Lightweight phased array antennas having a wide frequency bandwidth and a wide scan angle can be economically manufactured and conformally mounted on a surface, such as a nose cone of an aircraft. Examples of such antenna include a current sheet array (CSA) formed of at least one dipole layer and using coupling capacitors between antenna dipole elements. The capacitors often are formed as interdigitated “fingers.” The coupling capacitance between dipole elements can be increased by lengthening the capacitor “digits” or “fingers,” which results in additional bandwidth for the antenna. An example of this type of structure is disclosed in commonly assigned U.S. Pat. No. 6,417,813 to Durham, the disclosure which is hereby incorporated by reference in its entirety.
A similar phased array antenna is disclosed in commonly assigned U.S. Pat. No. 6,822,616 to Durham et al., which overcomes the significant gain drop-out with some frequencies at a desired operational bandwidth. That disclosed antenna provides a lightweight phased array antenna with a wide frequency bandwidth and wide scan angle that is still conformally mountable on a surface and not subject to a gain drop-out. It can include a feed-through lens antenna to replicate an electromagnetic (EM) environment, and provide a high pass filter response. As disclosed in the '813 and '616 patents, the antenna is a connected array that relies on capacitive coupling between adjacent dipole antenna elements.
Often these types of phased array antennas are formed as large arrays, often with subarrays, and operable in the 2.0 through 18.0 GHz range. They can be constructed from different modules with separate array panels, for example, each about 12×18 inches and forming an antenna aperture. They can be constructed with an interdigitated assembly of various beam former components, subarray beam formers, transmit/receive modules and associated components, with connections that are ribbon bonded to antenna feed portions and associated legs extending outward therefrom. The antenna elements form the dipoles. As a result, these phased array antenna structures have an array of tightly packed and closely spaced dipole elements connected to neighboring dipole elements through capacitor coupling, as set forth in the above-identified and incorporated by reference '616 and '813 patents. The antenna can have dual polarization by using horizontal and vertical dipole elements and solder connections at feed points. The capacitor coupling imparts a broadband performance, and can be formed using interdigitated or in some cases end-coupled capacitor elements. The interdigitated capacitor elements have lengthened “fingers” to increase capacitance. Increasing the length of fingers, however, can be problematic because the structure becomes resonant. Thus, edge coupling may be used.
Even with the performance advantages provided by this type of phased array antenna structure, it would be desirable to form the array in a manner that makes such arrays more easily repairable since entire arrays often must be scrapped if one antenna dipole element is defective.